Vehicle system with multiple electric drive axles

ABSTRACT

Methods and systems are provided for a vehicle system. In one example, the vehicle system includes a first electric drive axle assembly and a second electric drive axle assembly. Each of the first and second axle assemblies has a gear train with a planetary gear set axially offset from a motor-generator. Each planetary gear set is rotationally coupled to a differential.

FIELD

The present description relates generally to electric drive axles invehicles, and more particularly to a vehicle system including multipleelectric drive axles.

BACKGROUND

Electrified axles have been incorporated into electric as well as hybridvehicles to generate and/or augment vehicle propulsion. Drive axles havebeen provided in both the front and rear of the vehicles. For example,in certain vehicle designs, one drive axle receives rotational energyfrom an engine and another drive axle receives rotational energy from anelectric motor. Other axles system have utilized electric motors coupledto each drive wheel to provide four wheel drive operation.

However, the inventors have recognized that using multiple electrifiedaxles (e.g., a front and rear electric drive axle) in a vehicle maypresent challenges with regard to manufacturing costs, vehicle handling,axle structural integrity, as well as drive axle control. For example,providing a drivetrain with a separate electric motor for each drivewheel may significantly increase the drivetrain's manufacturing costs.The inventors have also recognized that cost reductions may be achievedby using similar components in multiple vehicle drive axles. However,vehicle packaging may, in certain cases, impede an identical electrifiedaxle housing from being used in both the front and rear of the vehicle.Furthermore, packaging constraints may lead to the re-orientation of thefront and rear drive axles, in some instances, presenting motor controlissues with regard to coordinated control of the different motors in thedrivetrain.

SUMMARY

To overcome at least some of the aforementioned drawbacks, a vehiclesystem is provided. In one example, the vehicle system includes a firstelectric drive axle assembly with a first gear train having a firstplanetary gear set axially offset from a first electric motor-generator,where the first planetary gear set is rotationally coupled to a firstdifferential. Further, the vehicle system has a second axle assemblywith a second gear train having a second planetary gear set axiallyoffset from a second electric motor-generator, where the secondplanetary gear set is rotationally coupled to a second differential.Arranging the gears in this manner allows the first and second electricdrive axle assemblies to achieve a space efficient arrangement.Consequently, the axles may be less susceptible to damage from roaddebris, obstacles, etc.

In another example, the first gear train may include multiple selectablegear sets rotationally coupled to the first planetary gear set and thesecond gear train includes multiple selectable gear sets rotationallycoupled to the second planetary gear set. At least a portion of thegears in the selectable gears sets in the first gear train may have asubstantially equivalent size in relation to corresponding gears in thesecond gear train. Using similar gear sizes in each of the drive axlesallows the manufacturing cost of the drive axle system to be reduced.

In yet another example, the first and second drive axle assemblies maybe oriented such that the first and second planetary gear sets arepositioned inboard or outboard from the first and second electricmotor-generators, correspondingly. In this example, the electricmotor-generators may be controlled to rotate in opposite directionsduring forward or reverse drive. In this way, front-rear motor controlis coordinated to implement forward or reverse vehicle drive modes.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a vehicle including a vehiclesystem.

FIG. 2 shows a perspective view of an example of a vehicle systemincluding multiple electric drive axle assemblies.

FIG. 3 shows a top-down view of a first arrangement of the front andrear electric drive axle assemblies.

FIG. 4 shows a top-down view of a second arrangement of the front andrear electric drive axle assemblies.

FIG. 5 shows a top-down view of a third arrangement of the front andrear electric drive axle assemblies.

FIG. 6 shows a top-down view of a fourth arrangement of the front andrear electric drive axle assemblies.

FIG. 7 shows a top-down view of a fifth arrangement of the front andrear electric drive axle assemblies.

FIG. 8 shows a top-down view of a sixth arrangement of the front andrear electric drive axle assemblies.

FIG. 9 shows an example of a routine for operating a vehicle equippedwith electric drive axle assemblies which may be any of the arrangementsof FIGS. 3-8 .

FIGS. 2-8 are shown approximately to scale. However, other relativedimensions may be used, in other embodiments.

DETAILED DESCRIPTION

A vehicle system with two electric drive axles is described herein.Different features of the vehicle system allow the system to achieve acompact design which may be less expensive to manufacture than previouselectrified axles. To elaborate, in one example, the orientation of afront electric drive axle relative to a rear electric drive axle may beselected to allow substantially equivalent gears in the drive axles tobe used while also meeting packaging constraints in the vehicle. Forinstance, planetary gear sets in each of the axles may be positionedinboard or outboard in relation to the electric motor-generators. In oneexample, the front axle housing may mirror the rear axle housing but thedirection of motor rotation in the front and rear electric motors may beequivalent during forward or reverse drive. In this way, the electricmotors can run in the same direction so the drive and coast flanks ofthe gears can be improved for forward drive, regeneration, and reversemodes. However, in such an example, in production, the front and rearaxle constituents may need separate part numbers and/or identifyingmarkers. In another example, the front axle housing and the rear axlehousing may have a similar geometric profile but the electric motors ineach axle may be positioned inboard or outboard with regard to a centralsection of the vehicle. In such an example, the direction of motorrotation in the front and rear electric motors may be opposite oneanother, during forward or reverse drive. In this way, motor control maybe coordinated to enable forward and reverse drive operation and allowthe housing of each axle to have an equivalent geometry to reduce systemmanufacturing costs.

FIG. 1 schematically illustrates a vehicle with a vehicle systemdesigned with multiple gear ratios. An example of the vehicle system,including a front axle assembly and a rear axle assembly, is shown inFIG. 2 from a perspective view. Various orientations of the front andrear axle assemblies are illustrated in FIGS. 3-8 . An example of aroutine for operating the electric drive axle assemblies which may beimplemented in the vehicle is depicted in FIG. 9 .

FIG. 1 shows a schematic depiction of a vehicle 100 having a vehiclesystem 102 with an electric drive axle assembly 103 including a geartrain 104 and an electric motor-generator 106. The stick diagram of FIG.1 provides a high-level topology of the vehicle, gear train, andcorresponding components. However, it will be understood that thevehicle, gear train, and corresponding components have greaterstructural complexity than is captured in FIG. 1 . The structuraldetails of various facets of the vehicle system 102 are illustrated, byway of example, in greater detail herein with regard to FIGS. 2-8 .

The electric motor-generator 106 is electrically coupled to an energystorage device 108 (e.g., battery, capacitor, and the like). Arrows 109signify the energy transfer between the electric motor-generator 106 andthe energy storage device 108 that may occur during different modes ofsystem operation. The electric motor-generator 106 may includeconventional components for generating rotational output (e.g., forwardand reverse drive rotational output) and/or electrical energy forrecharging the energy storage device 108 such as a rotorelectromagnetically interacting with a stator, to provide theaforementioned energy transfer functionality. The electricmotor-generator 106 is shown including a rotor shaft 180 with a firstbearing 181 and a second bearing 182 coupled thereto. The first bearing181 may be a fixed bearing and the second bearing 182 may be a floatingbearing. Although the second bearing 182 is shown positioned within themotor-generator, it will be understood that in some embodiments, bearing182 may be coupled to the input shaft to facilitate rotation thereof.Other bearing arrangements with regard to the motor-generator have beencontemplated such as arrangements with alternate quantities and/or typesof bearings.

The vehicle may take a variety of forms in different embodiments. Forexample, the vehicle 100 may be hybrid vehicle where both the electricmotor-generator 106 and an internal combustion engine (not shown) areutilized for motive power generation. For instance, in one use-casehybrid vehicle configuration, the internal combustion engine may assistin recharging the energy storage device 108, during certain conditions.In another use-case hybrid vehicle configuration, the internalcombustion engine may be configured to provide rotational energy to adifferential 110 or other suitable locations in the gear train 104.Further, in other examples, the vehicle may be a battery electricvehicle (BEV) where the internal combustion engine is omitted.

The rotor shaft 180 of the electric motor-generator 106 is coupled to aninput shaft 112. For instance, the rotor shaft 180 may be transitionfit, slip fit, mechanically attached, in splined engagement,combinations thereof, etc., with an end of the input shaft 112. A firstgear 114 is positioned or formed on the input shaft 112. A bearing 183is shown coupled to the input shaft 112. The bearing 183 may be a fixedbearing, in one example. However, in other examples, the bearing 183 maybe another suitable type of bearing or in some cases may be omitted fromthe system.

A second gear 116 is rotationally coupled to the first gear 114 andresides on an intermediate shaft 118. As described herein, rotationalcoupling between gears or other components may include an interfacebetween the gears where teeth of the gears mesh to facilitate rotationalenergy transfer therebetween. As such, rotational coupling of thecomponents allows rotational energy transfer to be transferred betweenthe corresponding components. Conversely, rotational decoupling mayinclude a state between two components when rotational energy issubstantially inhibited from being transferred between the components.

A third gear 120 and a fourth gear 122 are additionally included on theintermediate shaft 118, although other gearing arrangements have beenenvisioned. Bearings 184 (e.g., tapered roller bearings) are coupled toeither axial end of the intermediate shaft 118 to support the shaft andfacilitate rotation thereof. The tapered roller bearings may decreasethe axle package width when compared to other types of bearing such asball bearings. However, other suitable intermediate shaft bearing typesand/or arrangements have been envisioned. The bearing arrangement on theintermediate shaft as well as the other bearing arrangements describedherein may be selected based on expected shaft loading (e.g., radial andthrust loading), gear size, shaft size, etc.

Continuing with the gear train description, the fourth gear 122 isrotationally coupled to a fifth gear 124 and the third gear 120 isrotationally coupled to a sixth gear 126. The first gear 114, the secondgear 116, the third gear 120, the fourth gear 122, the fifth gear 124,and the sixth gear 126 are included in a gear assembly 130, in theillustrated embodiment. However, the gear assembly may include analternate number of gears and/or have a different layout, in otherembodiments. The number of gears in the assembly and the assembly layoutmay be selected based on end-use design goals related to desired gearrange and packaging, for instance.

The first gear 114, the second gear 116, the fourth gear 122, and thefifth gear 124, may be included in a first gear set 127. Additionally,the first gear 114, the second gear 116, third gear 120, and the sixthgear 126, may be included in a second gear set 129. The first gear set127 may have a higher gear ratio than the second gear set 129, in oneexample. However, other gear arrangements in the different gear sets maybe used, in other examples. Clutch assemblies in the system 102 allowthe first gear set 127 or the second gear set 129 to be placed in anoperational state. To elaborate, the clutch assemblies allow the gearratio delivered to drive wheels 128 on driving surfaces 133, by way ofthe gear assembly 130, a planetary gear assembly 138, and thedifferential 110, to be adjusted. For instance, the clutch assembliesmay be operated to engage the first gear set 127, during certainconditions (e.g., towing, lower speed vehicle operation, etc.), andengage the second gear set 129, during other conditions (e.g., higherspeed vehicle operation). As such, the system may transition between thedifferent gear sets based on vehicle operating conditions, driver input,etc. In this way, the gear train has distinct selectable gear ratios,allowing the gear train to be adapted for different driving conditions,as desired. It will be appreciated that the gear ratio adjustability mayalso be utilized to increase electric motor efficiency, in some cases.

The system 102 may specifically include a first clutch assembly 132 anda second clutch assembly 134. The first clutch assembly 132 isconfigured to rotationally couple and decouple the fifth gear 124 froman output shaft 136. Likewise, the second clutch assembly 134 functionsto rotationally couple and decouple the sixth gear 126 from the outputshaft 136. The first clutch assembly 132 may include a one-way clutch185 (e.g., sprag clutch) and a locking clutch 186 working in conjunctionto accomplish the coupling/decoupling functionality, in a compactarrangement. However, other clutch designs have been contemplated, suchas a friction clutch (e.g., wet friction clutch), a hydraulic clutch, anelectromagnetic clutch, and the like.

The one-way clutch 185 may be designed to transfer rotational energyfrom the fifth gear 124 to the output shaft 136 when the fifth gear isrotating in the forward drive direction and the rotational speed exceedsthat speed of the output shaft. Conversely, when the fifth gear isrotating in the reverse drive direction of the output shaft speed isgreater than the fifth gear speed, the one-way clutch freewheels,allowing the fifth gear and the output shaft to be rotationallydecoupled. Furthermore, the locking clutch 186 may be configured torotationally couple and decouple the fifth gear from the output shaft.For instance, the locking clutch may be activated during a reverse drivemode or during a regeneration mode.

The second clutch assembly 134 may be a wet friction clutch providingsmooth engagement/disengagement between the sixth gear 126 and theoutput shaft 136, in one embodiment. However, in other examples, thesecond clutch assembly 134 may include additional or alternate types ofsuitable clutches (e.g., hydraulic, electromagnetic, etc.).

The output shaft 136 is rotationally coupled to the planetary gearassembly 138, in the illustrated embodiment. The planetary gear assembly138 may include an annulus 187 also referred to as a ring gear, acarrier 188 with planet gears 189 mounted thereon, and a sun gear 190providing a space efficient design capable of providing a relativelyhigh gear ratio in comparison to non-planetary arrangements. However,non-planetary gear layouts may be used in the system, in certainembodiments, when for example, space efficient packaging is lessfavored. In the illustrated embodiment, the sun gear 190 is rotationallycoupled to the output shaft 136 and the carrier 188 is rotationallycoupled to the differential 110 (e.g., a differential case). However, inalternate examples, different gears in the planetary assembly may berotationally coupled to the output shaft and the differential. Further,in one example, the components of the planetary gear assembly 138 may benon-adjustable with regard to the components that are held stationaryand allowed to rotate. Thus, in one-use case example, the annulus 187may be held substantially stationary and the carrier 188, planet gears189, and the sun gear 190 and the gears stationary/rotational state mayremain unchanged during gear train operation. In the illustratedembodiment, the annulus 187 is fixedly coupled to the motor-generatorhousing, to increase system space efficiency. However, the annulus maybe fixedly coupled to other vehicle structures, in other instances. Byusing a non-adjustable planetary assembly, gear train operation may besimplified when compared to planetary arrangements with gears havingrotational state adjustability. However, adjustable planetaryarrangements may be used in the system, in other embodiments.

Various bearings may be coupled to the output shaft 136 and theplanetary gear assembly 138 to enable rotation of components coupled tothe shaft and assembly and in some cases support the components withregard to radial and/or thrust loads. A bearing 191 (e.g., needle rollerbearing) is shown coupled to the output shaft 136 and the second clutchassembly 134. Additionally, a bearing 192 (e.g., tapered roller bearing)is shown coupled to the second clutch assembly 134. A bearing 193 (e.g.,floating bearing) is also shown coupled to the second clutch assembly134 and the output shaft 136. A bearing 194 (e.g., thrust bearing) mayalso be positioned axially between and coupled to the sixth gear 126 andthe first clutch assembly 132. A bearing 196 (e.g., fixed bearing) mayalso be coupled to the one-way clutch 185. Additionally, a bearing 197(e.g., ball bearing) is shown coupled to the planetary gear assembly 138and a bearing 198 (e.g., ball bearing) is shown coupled to thedifferential case 142. However, other suitable bearing arrangements havebeen contemplated, such as arrangements where the quantity and/orconfigurations of the bearings are varied.

Additionally, FIG. 1 depicts the planetary gear assembly 138 directlyrotationally coupled to the differential 110. Directly coupling theplanetary gear assembly to the differential increases system compactnessand simplifies system architecture. In other examples, however,intermediate gearing may be provided between the planetary gear assemblyand the differential. In turn, the differential 110 is designed torotationally drive an axle 140 coupled to the drive wheels 128. The axle140 is shown including a first shaft section 141 and a second shaftsection 143 coupled to different drive wheels 128. Furthermore, the axle140 is shown arranged within (e.g., co-axial with) the output shaft 136which allows more space efficient design to be achieved. However, offsetaxle-output shaft arrangements may be used, in other examples.

Further in one example, the axle 140 may be a beam axle. A beam axle,also referred to in the art as a solid axle or rigid axle, may be anaxle with mechanical components structurally supporting one another andextending between drive wheels coupled to the axle. Thus, wheels coupledto the axle may move in unison when articulating, during, for example,vehicle travel on uneven road surfaces. For instance, the beam axle maybe a structurally continuous axle spanning the drive wheels on a lateralaxis, in one embodiment. In another embodiment, the beam axle mayinclude co-axial shafts receiving rotational input from different gearsin the differential and structurally supported by the differential.

The differential 110 may include a case 142 housing gearing such aspinion gears, side gears, etc., to achieve the aforementioned energytransfer functionality. To elaborate, the differential 110 may be anelectronic locking differential, in one example. In another example, thedifferential 110 may be an electronic limited slip differential or atorque vectoring dual clutch. In yet other examples, an opendifferential may be used. Referring to the locking differential example,when unlocked, the locking differential may allow the two drive wheelsto spin at different speeds and conversely, when locked, the lockingdifferential may force the drive wheels to rotate at the same speed. Inthis way, the gear train configuration can be adapted to increasetraction, under certain driving conditions. In the case of the limitedslip differential, the differential allows the deviation of the speedbetween shafts 144 coupled to the drive wheels 128 to be constrained.Consequently, traction under certain road conditions (e.g., low tractionconditions such as icy conditions, wet conditions, muddy conditions,etc.) may be increased due to the wheel speed deviation constraint.Additionally, in the torque vectoring dual clutch example, thedifferential may allow for torque delivered to the drive wheels to beindependently and more granularly adjusted to again increase tractionduring certain driving conditions. The torque vectoring dual clutch maytherefore provide greater wheel speed/torque control but may, in somecases, be more complex than the locking or limited slip differentials.

The vehicle 100 may also include a control system 150 with a controller152. In some examples, as described herein with reference to FIGS. 3-9 ,the vehicle system 102 may include more than one electric drive axleassembly. As such, the electric drive axle assembly 103 including thegear train 104, electric motor-generator 106, etc., may be a rearelectric drive axle assembly, in one use-case. In such a use-case, asimilar electric drive axle assembly may be provided at the front axlewhich includes a similar gear train, electric motor-generator, etc.Thus, in some embodiments, the front and rear electric drive axleassemblies may each include gear trains with similar gear ratios andclutches enabling gear ratio selection functionality. Both the first andsecond electric drive axle assemblies may be controlled by the controlsystem 150 and controller 152. In addition, in some examples, themotor-generator of each drive axle may be coupled to the energy storagedevice 108. In other examples, each motor-generator may be coupled to anindividual energy storage device.

The controller 152 includes a processor 154 and memory 156. The memory156 may hold instructions stored therein that when executed by theprocessor cause the controller 152 to perform the various methods,control techniques, etc., described herein. The processor 154 mayinclude a microprocessor unit and/or other types of circuits. The memory156 may include known data storage mediums such as random access memory,read only memory, keep alive memory, combinations thereof, etc.Furthermore, it will also be understood that the memory 156 may includenon-transitory memory.

The controller 152 may receive various signals from sensors 158 coupledto various locations in the vehicle 100 and the vehicle system 102. Thesensors may include a motor-generator speed sensor 160, an energystorage device temperature sensor 162, an energy storage device state ofcharge sensor 164, wheel speed sensors 166, clutch position sensors 168,etc. The controller 152 may also send control signals to variousactuators 170 coupled at different locations in the vehicle 100 and thevehicle system 102. For instance, the controller 152 may send signals tothe electric motor-generator 106 and the energy storage device 108 toadjust the rotational speed and/or direction (e.g., forward driverotational direction and reverse drive rotational direction) of themotor-generator. The controller 152 may also send signals to the firstclutch assembly 132 and the second clutch assembly 134 to adjust theoperational gear ratio in the gear train 104. For instance, the firstclutch assembly 132 may be disengaged and the second clutch assembly 134may be engaged to place the second gear set 129 in an operational state(transferring rotational energy between the electric motor-generator 106and the output shaft 136). The other controllable components in thevehicle and gear system may function in a similar manner with regard tocommand signals and actuator adjustment. For instance, the differential110 may receive command signals from the controller 152.

The vehicle 100 may also include an input device 172 (e.g., a gearselector such as a gear stick, gear lever, etc., console instrumentpanel, touch interface, touch panel, keyboard, combinations thereof,etc.) The input device 172, responsive to driver input, may generate amode request indicating a desired operating mode for the gear train. Forinstance, in a use-case example, the driver may shift a gear selectorinto a gear mode (e.g., first gear mode or second gear mode) to generatea gear set modal transition request at the controller. In response, thecontroller commands gear train components (e.g., the first clutchassembly 132 and the second clutch assembly 134) to initiate atransition into a first gear mode, where the first gear set 127 isoperational, from a second gear mode, where the second gear set 129 isoperational, or vice versa. The controller 152 may also be configured totransition the vehicle system 102 into a regenerative mode. In theregenerative mode energy is extracted from the gear train using theelectric motor-generator 106 and transferred to the energy storagedevice 108. For instance, the electric motor-generator 106 may be placedin a generator mode configured to convert at least a portion of therotational energy transferred from the drive wheels to the generator byway of the gear train into electrical energy. It will be appreciatedthat the other electric drive axle assembly included in the vehicle maybe operated in similar modalities, in some embodiments.

FIG. 2 shows a vehicle system 200 of a vehicle 210. It will beappreciated that the vehicle system 200, shown in FIG. 2 , serves as anexample of the vehicle system 102 shown in FIG. 1 . As such, at least aportion of the functional and structural features of the vehicle system102 shown in FIG. 1 may be embodied in the vehicle system 200 shown inFIG. 2 or vice versa, in certain embodiments.

The vehicle system 200 includes a first electric drive axle assembly 202and a second electric drive axle assembly 204. A set of reference axes201 are provided for reference in FIGS. 2-8 , indicating a y-axis, anx-axis, and a z-axis. The z-axis may be a longitudinal axis, the x-axismay be a lateral axis, and/or the y-axis may be a vertical axis, in oneexample. However, the axes may have other orientations, in otherexamples.

As one example, the first electric drive axle assembly 202 may be afront electric drive axle of the vehicle 210 and the second electricdrive axle assembly 204 may be a rear electric drive axle of the vehicle210. In one example, the front axle may be a beam axle coupled to frontdrive wheels 203 of the vehicle 210 and the rear axle may also be a beamaxle coupled to rear drive wheels 205 of the vehicle 210. Therefore, insuch an example, the front electric drive axle assembly 202 may bearranged proximate to a front end 206 of the vehicle 210 and the rearelectric drive axle assembly 204 may be arranged proximate to a rear end208 of the vehicle 210.

Components of the front electric drive axle assembly 202 will now bedescribed. It will be appreciated that, although positioned in adifferent orientation, the rear electric drive axle assembly 204 may besimilarly configured to the front electric drive axle assembly 202, withregard to internal componentry such as gearing, clutches, electric motorgenerators, etc.) and as such, description of the components of thefront electric drive axle assembly 202 may be applicable to componentsof the rear electric drive axle assembly 204. Details of the relativeorientations of the front electric drive axle assembly 202 and the rearelectric drive axle assembly 204 are provided further below withreference to FIGS. 3-8 .

The front electric drive axle assembly 202 includes a first electricmotor-generator with a rotor shaft 213 connected to a first input shaft214. The first electric motor-generator is omitted in FIG. 2 for butdepicted in FIGS. 3-8 . It will be appreciated that other suitableelectrical interfaces other than the electrical interface shown in FIGS.3-8 may be used, in other examples. The first motor-generator may becoupled to a first gear train 212 which may include the first inputshaft 214, a first intermediate shaft 216, and a first output shaft,obscured from view in FIG. 2 .

The first input shaft 214 receives rotational input (forward or reversedrive rotation) from the rotor shaft 213 of the first electricmotor-generator, while the system is operating in forward and reversedrive modes. The first input shaft 214 is rotationally coupled to thefirst intermediate shaft 216 and the first output shaft by way of thefirst gear train 212. Rotational axes 222, 224, and 226 of the firstinput shaft 214, the first intermediate shaft 216, and the first outputshaft, respectively, are provided for reference in FIG. 2 . FIG. 2additionally shows a first planetary gear assembly 228 rotationallycoupled to a first differential 230 in the first gear train 212. It willbe appreciated that placing the first planetary gear assembly 228 nextto the first differential 224 allows less torque to be carried throughthe first gear train 212, enabling the drive train to have fewer and/orsmaller components, if wanted.

The first planetary gear assembly 228 can achieve a targeted gear ratio(e.g., a relatively high gear ratio, such as a ratio greater than 20:1,in one use-case) in a compact arrangement relative to non-planetary geararrangements. Thus, the planetary gear assembly can achieve a desiredgear ratio with less components (e.g., gears and shafts) thannon-planetary gear assemblies, if desired. Furthermore, in embodimentswhere the planetary gear assembly exhibits a relatively high torqueoutput, the planetary assembly can attain a more compact packaging dueto the load sharing between the planet gears, if desired.

The first gear train 212 includes a gear assembly 289 that may includesix gears (a first gear 290, a second gear 291, a third gear (obscuredfrom view), a fourth gear 292, a fifth gear 293, and a sixth gear 294),where the second, third, and fourth gears are coupled to the firstintermediate shaft 216, as described above with regard to FIG. 1 . Thefifth and sixth gears are coupled to the first output shaft. It will beunderstood, that during different modes of system operation differentsets of gears may be operational. The first, second, fourth, and fifthgears may be included in a first gear set and the first gear, second,third, and sixth gears may be included in a second gear set, asdescribed above for FIG. 1 . A park gear may also be included in thefirst gear train 212, in some examples. However, the gear sets mayinclude different gear combinations, in other examples.

It will also be understood that the first and the second gear sets havedifferent gear ratios. In this way, the gear train may include multiplegear ratios to increase gear train adaptability. Additionally, the gearsets may share a few common gears (i.e., the first and second gears inthe illustrated embodiment). Fixing the first ratio (i.e., the first andsecond gears) in the gear train can allow the accuracy of the gears tobe increased, if wanted, thereby reducing noise, vibration, andharshness (NVH) in the system. However, embodiments where the gear setsdo not include overlapping gears have been envisioned. Clutchassemblies, which may be similar to the clutch assemblies 132 and 134shown in FIG. 1 , are included in the first gear train 212 to enable thefirst gear set and the second gear set to be coupled/decoupled to/fromthe first output shaft. In this way, the different gear sets may beoperationally selected to, for example, more aptly suite the drivingenvironment and/or increase electric motor efficiency. Thus, the firstand second gear sets may be conceptually included in a selectable gearassembly.

The first planetary gear assembly 228 is rotationally coupled to thefirst output shaft and the first differential 230 in the first geartrain 212 is rotationally coupled to the first planetary gear assembly228. However, other gear layouts may be used in other examples, such asnon-planetary gear assemblies, gear trains with gears positioned betweenthe planetary assembly and the differential, etc. The first planetarygear assembly 228 allows a desired gear ratio to be realized in acompact arrangement. For instance, the first planetary gear assembly 228may achieve a relatively high gear ratio and space efficiency, ifdesired. However, non-planetary gear arrangements may be used, in otherexamples.

Furthermore, the first planetary gear assembly 228 and the firstdifferential 230 are shown positioned on a lateral side relative to thefirst motor-generator (e.g., where the first motor-generator is coupledto the first input shaft 214 and centered about the rotational axis 222of the first input shaft 214). In other words, the first planetary gearassembly 228 and the first differential 230 are positioned on lateralside of the first motor-generator along the z-axis. More specifically,the first planetary gear assembly 228 and the first differential 230 areaxially offset from the rotor shaft 313 of the first motor-generator.Therefore, the rotational axis 222 of the rotor shaft 213 is notco-axial with the rotational axis 226 of the output shaft, the firstplanetary gear assembly 228, and the first differential 230. It will beappreciated that the first planetary gear assembly 228 may be axiallyoffset from the first motor-generator due to the planetary gearassembly's ability to be integrated into the gear train without a matinggear parallel thereto, if wanted. In this way, the planetary gearassembly may be placed in a space which has remained unused in certainelectrified gearboxes. Thus, positioning the planetary gear assembly onthe side of the motor allows the compactness of the axle system to beincreased. As a result, the packaging constraints arising during axleinstallation in the vehicle may pose less of an issue. However, in otherexamples, the first planetary gear assembly 228 may be positioned inother suitable locations.

As described above, the vehicle system 200 includes two electric driveaxle assemblies. In the illustrated embodiment, each electric drive axleassembly has substantially similar gear components (e.g., gear shafts,gears, and/or clutches). To elaborate, the gears in the front electricdrive axle assembly 202 and the second electric drive axle assembly 204may include individual gears in their respective gear trains that aresubstantially equivalent in size and/or profile. For instance,equivalent gears may have a similar inner diameter, outer diameter,width, and/or tooth pattern. Thus, the gears may be jointly manufacturedto allow for reductions in vehicle manufacturing costs. However, inother examples, only a portion of the gears and/or other components ineach drive axle may have a substantially equivalent size and/or profile.

Therefore, as shown in FIG. 2 , the rear electric drive axle assembly204 also includes a second gear train 250, a second input shaft 252, asecond intermediate shaft 254 and a second output shaft 256. A secondmotor-generator with a rotor shaft 257 may be connected to the secondinput shaft 252. The second motor-generator may be axially (e.g., alongthe x-axis) offset from a second planetary gear assembly 258 and asecond differential 260 of the second gear train 250. Furthermore, thegears in the second gear train 250 are shown including six gears (afirst gear 295, a second gear 296, a third gear 297, a fourth gear(obscured from view), a fifth gear 298, and a sixth gear 299). However,as mentioned above, the gear trains may have an alternate number ofgears, in other embodiments.

Components of the rear electric drive axle assembly 204 may be orientedin a similar, or equivalent, arrangement relative to one another as thefront electric drive axle assembly 202. However, relative to the frontend 206 and rear end 208 of the vehicle 210, the rear electric driveaxle assembly 204 and the front electric drive axle assembly 202 mayeach be positioned such that their respective motor generator rotorshafts (213 and 257) are positioned outboard with regard to a centralvehicle region 259. Thus, in such an example, the orientations of therear electric drive axle assembly 204 and the front electric drive axleassembly 202, shown in FIG. 2 , are rotated 180° about the y-axis withregard to one another. Although, the vehicle 210 is shown in anarrangement where the rotor shafts are positioned in an outboardlocation, it will be appreciated that the front and rear electric driveaxle assemblies 202 and 204 may be positioned in different orientations,in other embodiments. FIGS. 3-8 depict different possible orientationsof front and rear drive axles in the vehicle system 200 with the driveaxle's componentry enclosed in outer housings. It will also beunderstood, that the vehicle system 200 and the other vehicle systemarrangements described herein may be controlled by a suitablecontroller, such as the controller 152, shown in FIG. 1 .

FIG. 3 shows a first vehicle system arrangement 300. As shown in FIG. 3, the first vehicle system arrangement 300 includes a front electricdrive axle assembly 302, providing torque to front drive wheels 303 ofthe vehicle 210, and a rear electric drive axle assembly 304, providingtorque to rear drive wheels 305. As previously discussed, each electricdrive axle assembly may include axles 390, 392 with axle shafts coupledto a differential and the drive wheels.

In the illustrated embodiment, the rear electric drive axle assembly 304is rotated 180° about the y-axis relative to the front electric driveaxle assembly 302 so that a first motor-generator 306 of the frontelectric drive axle assembly 302 and a second motor-generator 308 of therear electric drive axle assembly 304 are positioned in an outboardconfiguration. In the outboard configuration of the first vehicle systemarrangement 300, each of the first motor-generator 306 and the secondmotor-generator 308 are spaced away from a central region 310 of thevehicle 210. The central region 310, may be longitudinally bounded, inone example, by front and rear axles 390 and 392 extending between thefront and rear drive wheels 303, 305, respectively.

The front electric drive axle assembly 302 is depicted with a firstouter housing 312 and the rear electric drive axle assembly 304 isdepicted with a second outer housing 314. The first and second outerhousings 312, 314 may enclose the first and second motor-generators 306,308 as well as a first gear train (e.g., the first gear train 212, shownin FIG. 2 ) and a second gear train (e.g., the second gear train 250,shown in FIG. 2 ), respectively. The first and second outer housings312, 314 may be similarly configured and the following description ofthe outer housing is applicable to both.

Each of the first and second outer housings 312, 314 may include a firstsection 350, a second section 352, a third section 354, and a fourthsection 356. It will be appreciated that each of the front and reardrive axle assemblies shown in FIGS. 4-8 include an outer housing havingsimilar sections to the first and outer housing 312, 314, described forFIG. 3 and will not be re-introduced for brevity. However, the relativepositions and orientations of the housing sections may vary between thedifferent vehicle system arrangements, shown in FIGS. 4-8 . Further, insome embodiments, the axle housings may have a mirrored profile fromfront to rear, as discussed in greater detail herein with regard to thevehicle system arrangements shown in FIGS. 5-6 .

The sections of the outer housings may be configured to be removablycoupled via fasteners, interference fitting, clamps, etc., to allowaccess to inner components of the vehicle system 200. To elaborate, thefirst section 350 may be coupled to the second section 352 at anattachment interface 380 and the third section 354 may be coupled to thefirst section 350 at an attachment interface 382. The first section 350may at least partially enclose portions of the motor-generator, thedifferential (e.g., the first differential 230, shown in FIG. 2 ), andthe gear train (e.g., the first gear train 212, shown in FIG. 2 ) of theaxle assembly. The second section 352 may at least partially surround aportion of the gear train and, when coupled to the first section 350.Additionally, the third section 354 may at least partially enclose andprovide access to the planetary gear assembly (e.g., the first planetarygear assembly 228, shown in FIG. 2 ) and the differential (e.g., thefirst differential 230, shown in FIG. 2 ).

The first section 350 of the outer housing may include a first shaftopening 358. It will be understood that a first section 394 of the rearaxle 392 coupled to one of the rear drive wheels 305 (or one of thefront drive wheels 303) of the vehicle 210 may extend through the firstshaft opening 358. The second section 352 of the outer housing mayinclude a second shaft opening 360. Again, a second section 396 of therear axle 392, coupled to one of the rear drive wheels 305 (or one ofthe front drive wheels 303), may extend through the second shaft opening360. Furthermore, it will be appreciated that the shaft openings in theaxle housings may be arranged co-axial with the output shafts (e.g.,output shaft 136, shown in FIG. 1 ) in the gear trains.

When assembled (e.g., all sections of the outer housing are coupled toone another) the outer housing provides an outer shell to the axleassembly and shields inner components of the axle assembly from contactwith flying debris during vehicle navigation.

In the first vehicle system arrangement 300, the front and rear axleassemblies 302, 304 are in the outboard configuration, as describedabove. In this arrangement, the first shaft opening 358 of the firstouter housing 312 is proximate to a first vehicle frame section 370 ofthe vehicle 210 (e.g., on the left side of FIG. 3 ), and the secondshaft opening 360 of the first outer housing 312 is proximate to asecond vehicle frame section 372 of the vehicle 210 (e.g., on the rightside of FIG. 3 ). Thus, the first and second housings may beinterchangeable and manufactured based on a single prototype, therebydecreasing manufacturing costs, if desired.

Each of the first and second motor-generators 306, 308 also includes anelectrical interface 307 protruding upwards from the motor-generators,along the y-axis. The electrical interface 307 allows electrical cablesto be connected to the motor-generators. Although the gear trains in thefront and rear electric drive axle assemblies 302, 304 may be similarlyconfigured (e.g., components of each gear train are similarly alignedand positioned relative to one another) a drive direction of the geartrains may be different. For example, as shown in FIG. 2 , a forwarddirection of the vehicle 210 is indicated by arrow 262. Both the frontdrive wheels 203 and the rear drive wheels 205 rotate in a firstdirection, as indicated by arrows 264, to enable forward navigation ofthe vehicle 210. To facilitate the rotation of the front drive wheels203 in the first direction for forward motion of the vehicle, the firstinput shaft 214 may be driven by the first motor-generator to rotate ina clockwise (cw) direction, as indicated by arrow 266, when viewing thefront electric drive axle assembly 202 along arrow 207. The firstintermediate shaft 216 may be driven by the first input shaft 214 torotate in a counterclockwise (ccw) direction, as indicated by arrow 268.Rotation of the first intermediate shaft 216 in the ccw direction may,in turn, drive rotation of the first output shaft 218 in the cwdirection, as indicated by arrow 270. As a result of the rotation of thefirst output shaft 218, the drive wheel 203 propel the vehicle 210 inthe forward direction, indicated via arrow 262.

As shown in FIG. 2 , at the rear axle of the vehicle 210, in a forwarddrive mode, components of the rear electric drive axle assembly 204 maybe configured to rotate in opposite directions in relation to componentsof the front electric drive axle assembly 202 due to the rotatedconfiguration of the front and rear electric drive axles. For example,when viewing the rear electric drive axle assembly 204 along arrow 209,the second input shaft 252 may be driven by the second motor-generatorto rotate in the ccw direction, as indicated by arrow 270, the secondintermediate shaft 254 may rotate in the cw direction, as indicated byarrow 272, and the second output shaft 256 may rotate in the ccwdirection, as indicated by arrow 274. As a result of the rotation of thesecond output shaft 256, the drive wheel 205 propel the vehicle 210 inthe forward direction, indicated via arrow 262.

As such, the first vehicle system arrangement 300, as shown in FIG. 3 ,the first motor-generator 306, and the second motor-generator 308 maygenerate opposite rotational outputs to achieve both forward and reversemotion of the vehicle 210. As such, a controller (e.g., the controller152 of FIG. 1 ) may be configured with instructions specific to thearrangement of the vehicle system 200 to accommodate the relativeorientations of the front and rear electric drive axle assemblies. Thus,when the vehicle system 200 is configured in the first vehicle systemarrangement 300, the controller of the vehicle 210 may be adapted withexecutable instructions to operate the first motor-generator and thesecond motor-generator in opposite rotational directions to achieveforward and reverse vehicle drive modes. It will also be understood,that during regeneration modes in both the front and rear electricmotor-generators the rotational input received by each motor-generatormay be in an opposite rotational direction.

In the outboard orientation of the front and rear electric drive axleassemblies (e.g., where the first and second motor-generators arerotated away from the central region 310 of the vehicle 210) thearrangement of the motor-generators may allow vehicle components (e.g.,battery banks, frame sections, etc.) to be efficiently located in thecentral region 310 with regard to space. Thus, by positioning themotor-generators away from the central region, motor-generator packagingmay not interfere with the centrally located vehicle components.Furthermore, positioning the electrical interfaces 307 on upper sides ofthe motor-generators decreases their exposure to road debris, stationaryobjects, etc., decreasing the chance of damage to the electricalinterfaces during vehicle operation.

In other instances, when space is available in the central region 310 ofthe vehicle 210, the motor-generators may be rotated inwards in aninboard configuration. For example, as shown in FIG. 4 , a frontelectric drive axle assembly 402 and a rear electric drive axle assembly404 may oriented such that they are rotated 180° about the y-axis inrelation to one another in a second vehicle system arrangement 400. Inthe second vehicle system arrangement 400, a first motor-generator 406of the front electric drive axle assembly 402 and a secondmotor-generator 408 of the rear electric drive axle assembly 404 arepositioned in an inboard configuration where the first and secondmotor-generators 406, 408 are in the central vehicle region 310. Aspreviously discussed, the central vehicle region 310 may belongitudinally bounded via the front and rear axles extending betweenthe drive wheels 303 and the drive wheel 305, respectively.

In the second vehicle system arrangement 400, the first shaft opening358 of a first outer housing 450 of the front electric drive axleassembly 402 may be proximate to the second vehicle frame section 372and the second shaft opening 360 of the first outer housing 450 may beproximate to the first vehicle frame section 370. The first shaftopening 358 of a second outer housing 452 of the rear electric driveaxle assembly 404 may be proximate to the first vehicle frame section370 and the second shaft opening 360 of the second outer housing 452 maybe proximate to the second vehicle frame section 372. Thus, the outerhousings in the second vehicle system arrangement 400 and the firstvehicle system arrangement 300 of FIG. 3 are oriented opposite oneanother.

In the second vehicle system arrangement 400, by positioning the firstand second motor-generators in an inboard region (e.g., the centralregion 310) a likelihood of contact between the motor-generators andflying debris may be decreased. Therefore, the motor-generators may bemore shielded in the inboard configuration of FIG. 4 than the outboardconfiguration of FIG. 3 .

Similar to the first vehicle system arrangement 300 of FIG. 3 , thefront electric drive axle assembly 402 may be equivalently configured tothe rear electric drive axle assembly 404 (e.g., positioning of a geartrain, planetary gear assembly, differential, and/or the geometry of anouter housing of the axle assemblies may be the same). To elaborate, thegear train of each electric drive axle assembly may each have aplurality of selectable gear sets which may be substantially equivalentto one another, in one embodiment. In this way, manufacturing costs ofthe vehicle system can be reduced, if desired. Electrical interfaces 403of each of the front and rear electric drive axle assemblies 402, 404may extend upwards, along the y-axis, from each of the axle assemblies.However, the first motor-generator 406 may be configured to rotate inopposite rotational directions than the second motor-generator 408 toachieve forward and reverse motion of the vehicle 210, as describedabove.

For example, when viewing the front electric drive axle assembly alongarrow 412, the first motor-generator 406 may spin in the ccw directionto achieve forward motion of the vehicle 210, as indicated by arrow 414.Viewing the second electric drive axle assembly 404 along arrow 416, anequivalent perspective relative to a geometry of the axle assemblies toarrow 412, the second motor-generator 408 may spin in the cw directionto similarly achieve forward motion of the vehicle 210. Conversely, whenreverse motion (e.g., vehicle motion is opposite of the directionindicated by arrow 414) of the vehicle 210 is desired, the firstmotor-generator 406 may spin in the cw direction and the secondmotor-generator 408 may spin in the ccw direction.

By implementing the first electric drive axle assembly and the secondelectric drive axle assembly of both the first and second arrangements300, 400 of FIGS. 3 and 4 with substantially equivalent configurations,a manufacturing of the axle assemblies may be simplified. A singleelectric drive axle assembly unit may, in some instances, be fabricatedand used for both the front and rear electric drive axle assembliestherefore precluding separate identification and packaging of frontversus rear axle assemblies.

In other examples, the vehicle system may have distinct front and rearelectric drive axle assembly housings. As shown in FIG. 5 in a thirdvehicle system arrangement 500, a front electric drive axle assembly 502and a rear electric drive axle assembly 504 may not be mirrored. Forexample, the front electric drive axle assembly 502 and the rearelectric drive axle assembly 504 may be mirror images across a mirrorplane 506, coplanar with the y-x plane. The layout of inner components,such as multiple selectable gear sets in each electric drive axleassembly, planetary gear sets, and differentials, of the axle assembliesmay also be mirrored. As such, the internal components may have asimilar form and size but a mirror arrangement. Thus, in such anexample, at least a portion of the inner components of the drive axleassemblies may be substantially equivalent. Put another way, theinternal gear train parts (e.g., gears, shafts, etc.) may be fabricatedwith manufacturing equivalency where the inner components may beconstructed using an analogous manufacturing process to producecomponents having substantially similar sizes, profiles, and materialconstructions. It will be appreciated, however, that relatively smalldimensional variances and other minor inconsistencies resulting from thetype of manufacturing process may be present in components having amanufacturing equivalency. In this way, the manufacturing cost of thevehicle system can be reduced.

A first outer housing 508 of the front electric drive axle assembly 502may be manufactured (e.g., cast, machined, etc.) as a mirror image of asecond outer housing 510 of the rear electric drive axle assembly 504.Thus, the first and second outer housings 508, 510 may have differentgeometric profiles. For example, as shown in FIG. 5 , the first shaftopening 358 of the first outer housing 508 may be proximate to thesecond vehicle frame section 372 and the second shaft opening 360 of thefirst outer housing 508 may be proximate to the first vehicle framesection 370. The first shaft opening 358 of the second outer housing 510is also proximate to the second vehicle frame section 372 and the secondshaft opening 360 of the second outer housing 510 is also proximate tothe first vehicle frame section 370. However, a first motor-generator512 of the front electric drive axle assembly 502 is positioned on anopposite side of the first and second shaft openings 358, 360 than asecond motor-generator 514 of the rear electric drive axle assembly 504.

The inner components may be arranged within the first housing 508 in anopposite orientation from inner components enclosed in the secondhousing 510. As such, the first motor-generator 512 of the frontelectric drive axle assembly 502 may be configured to spin in the samedirection as a second motor-generator 514 of the rear electric driveaxle assembly 504 to achieve forward and reverse propulsion of thevehicle 210.

For example, when viewing the front and rear electric drive axleassemblies 502, 504 from an equivalent perspective relative to thegeometries of the electric drive axle assemblies along arrow 516, thefirst motor-generator 512 may rotate in the ccw direction to rotate thefront drive wheels 303 of the vehicle 210 also in the ccw direction toenable forward travel of the vehicle 210, as indicated by arrow 414. Thesecond motor-generator 514 may also spin in the ccw direction to rotatethe rear drive wheels 305 of the vehicle 210 in the ccw direction.Executable instructions implemented at the controller of the vehicle 210may be simplified relative to the arrangements of FIGS. 3 and 4 tooperate the first and second motor-generators 512, 514 in the samerotational direction for forward and reverse motion of the vehicle 210.

In addition, the mirrored configuration of the vehicle system 200 mayallow drive and coast flanks of the gear trains of both the front andrear electric drive axle assemblies 502, 504 to be improved (e.g.,optimized) for drive, regeneration, and reverse modes of vehicleoperation. As mentioned above, when the front-rear electric drive axlesare mirror the motor-generator may be rotated in a similar direction inforward and reverse drive modes. However, with regard to manufacturing,separate parts numbers and/or identifying markers may be needed when themirrored configuration is implemented. Thus, gears, shafts, etc., offront and rear axles of the vehicle 210 may be manufactured withseparate part numbers and identifying markers, in some cases.

In the third vehicle system arrangement 500, the front and rear electricdrive axle assemblies 502, 504 are positioned in the outboardconfiguration where the first and second motor-generators 512, 514 arerotated away from the central region 310 of the vehicle 210. Electricalinterfaces 503 of both the electric drive axle assemblies may extendupwards, along the y-axis, from the electric drive axle assemblies. Thethird vehicle system arrangement 500 may be implemented when operationof the motor-generators in the same rotational direction is desiredwhile the central region 310 of the vehicle 210 is occupied by othervehicle components. In instances where space in the central region 310is available, the vehicle system 200 may be arranged in the inboardconfiguration while maintaining the mirrored orientation of the electricdrive axle assemblies, as shown in FIG. 6 .

FIG. 6 shows a fourth vehicle system arrangement 600. Similar to thethird arrangement of FIG. 5 , a front electric drive axle assembly 602and a rear electric drive axle assembly 604 are mirrored. Electricalinterfaces 603 of both axle assemblies extend upwards, along the y-axis.The fourth vehicle system arrangement 600 includes orienting the frontand rear axle assemblies 602, 604 in the inboard configuration where theaxle assemblies are rotated so that a first motor-generator 606 of thefront electric drive axle assembly 602 and a second motor-generator 608of the rear electric drive axle assembly 604 are situated in the centralregion 310 of the vehicle. In this way, the first and secondmotor-generators 606, 608 may be spun in the same rotational directionto compel forward or reverse drive of the vehicle 210, as well asactivation of a regeneration mode, while maintaining themotor-generators in a position which reduces interactions between roaddebris and the motor-generators during vehicle motion.

In an alternate configuration of the vehicle system 200, the electricdrive axle assemblies may have a same orientation in the vehicle. Forexample, FIG. 7 shows a fifth vehicle system arrangement 700, includinga front electric drive axle assembly 702 and a rear electric drive axleassembly 704. The axle assemblies are oriented so that electricalinterfaces 703 extend upwards, along the y-axis from the axleassemblies. The front and rear axle assemblies 702, 704 havesubstantially equivalent geometries, with components of each electricdrive axle assembly configured similarly. In one example, the front andrear electric drive axle assemblies 702, 704 may be interchangeablewithout affecting operation of the axle assemblies.

The substantially equivalent geometries of the axle assemblies enables afirst motor-generator 706 of the front electric drive axle assembly 702and a second motor-generator 708 of the rear electric drive axleassembly 704 to be spun in a same rotational direction to achieveforward motion, as indicated by arrow 414, or reverse motion of thevehicle 210. A single electric drive axle assembly unit may bemanufactured and applied to both the front axle and rear axle of thevehicle 210, thereby providing a simplified manufacturing process toimplement the fifth vehicle system arrangement 700 of FIG. 7 (as well asa sixth vehicle system arrangement 800 shown in FIG. 8 ) in the vehicle210 compared to the mirrored configurations of FIGS. 5 and 6 .Furthermore, operation of the electric drive axle assemblies in the samerotational direction allows control of the axle assemblies to bestreamlined compared to the rotated configurations of FIGS. 3 and 4 .

The front and rear electric drive axle assemblies 702, 704 are orientedin FIG. 7 so that the first motor-generator 706 is behind, relative tothe forward direction of motion indicated by arrow 710, an output shaftin a first gear train 712 of the front electric drive axle assembly 702and the second motor-generator 708 is behind an output shaft in a secondgear train 714 of the rear electric drive axle assembly 704. Asdescribed above, the output shafts of the gear trains are arrangedco-axial to the shaft openings 358 and the shaft openings 360. The firstmotor-generator 706 is positioned in the central region 310 of thevehicle 210 and the second motor-generator 708 is positioned proximateto a rear end of the vehicle. The fifth vehicle system arrangement 700may be used in a vehicle when space is available in the central region310 behind the front axle 390 but not in front of the rear axle 392.

Alternatively, the axle assemblies may be rotated 180° about the y-axisto be oriented opposite from the fifth vehicle system arrangement 700while maintaining the substantially equivalent and interchangeablegeometries of the axle assemblies. For example, as shown in FIG. 8 , asixth vehicle system arrangement 800 includes positioning a frontelectric drive axle assembly 802 and a rear electric drive axle assembly804 in a same orientation with electrical interfaces 803 of the axleassemblies extending upwards along the y-axis. As in the fifth vehiclesystem arrangement 700 of FIG. 7 , the front and rear axle assemblies802, 804 in the sixth vehicle system arrangement 800 may beinterchangeable. However, in the sixth vehicle system arrangement 800 ofFIG. 8 , the axle assemblies may be manufactured and assembled so that afirst motor-generator 806 is in front of an output shaft in a first geartrain 808 of the front electric drive axle assembly 802 relative to theforward direction of motion of the vehicle 210, as indicated by arrow414. Similarly, a second motor-generator 810 is positioned in front ofan output shaft of a second gear train 812 of the rear electric driveaxle assembly 804.

The second motor-generator 810 may be situated in the central region 310of the sixth vehicle system arrangement 800 and the firstmotor-generator 806 may be positioned proximate to a front end of thesixth vehicle system arrangement. Thus, the sixth vehicle systemarrangement 800 may be deployed when space is available in front of therear axle 392 in the central region 310 but not behind the front axle390.

In this way, an arrangement of the electric drive axle system may beselected based on a desired level of complexity of operation,manufacturing efficiency, packaging efficiency, and accommodation ofother vehicle components according to available packaging space. In eachof the vehicle system arrangements illustrated in FIGS. 3-8 , theelectric drive axle assemblies may be configured to maintain electricalinterfaces oriented upwards to maintain electrical cables away from theground and maintain a compact, space efficient footprint. The geartrains of each of the front and rear drive axle assemblies may havemanufacturing equivalency with substantially equivalent gear ratios inmultiple selectable gear sets of each gear train.

An example of a routine 900 for operating a vehicle equipped with any ofthe examples of a vehicle system, as shown in FIGS. 2-8 , is depicted inFIG. 9 . The vehicle system may include a first electric drive axleassembly, rotationally coupled to a front axle of the vehicle and asecond electric drive axle assembly, rotationally coupled to a rear axleof the vehicle. The front axle is attached to front drive wheels of thevehicle and the rear axle is attached to rear drive wheels of thevehicle. Each of the first and second axle assemblies includes anelectric motor-generator, a gear train, a planetary gear set and adifferential rotationally coupled to the planetary gear set. The axleassemblies may be coupled to the vehicle axles so that output shafts ofthe gear trains are co-axial with the vehicle axles and the planetarygear sets and differentials are axially offset from themotor-generators.

Additionally, in some embodiments, the gear trains of the first andsecond axle assemblies may have substantially equivalent selectable gearratios. The planetary gear sets of each of the gear trains may be bothpositioned longitudinally inboard from the motor-generators,longitudinally outboard from the motor-generators, or one planetary gearset may be longitudinally inboard from the corresponding motor-generatorand the other planetary gear set may be longitudinally outboard from thecorresponding motor-generator. Each of the first and axle assemblies mayhave outer housing which may have similar geometric profiles ordifferent geometric profiles. However, the axle assemblies may beoriented so that electrical interfaces of each assembly extends upwardsfrom the axle assemblies.

Routine 900 may be implemented when a change in vehicle operation modeoccurs, such as when forward or reverse motion of the vehicle isrequested from a stationary mode. Routine 900 may also be executedduring vehicle navigation (e.g., the vehicle is already in motion, and achange in speed is requested).

At 902, the routine includes adjusting operation of the motor-generatorsof the first and second electric drive axle assemblies. As an example,the vehicle may be stationary and the motor-generators may be inactive.Upon receiving a request for vehicle motion at a vehicle controller(e.g., as indicated by an accelerator pedal tip-in for example) thecontroller may command activation of the motor-generators to driverotation of the front and rear drive wheels. Alternatively the vehiclemay already be in motion and an increase or decrease in vehicle speedmay be indicated by a change in position of the accelerator pedal. Apower of the motor-generators may be adjusted accordingly.

Rotational energy is transferred from the motor-generators to the frontand rear drive wheels of the vehicle at 904. The energy may betransferred via rotation of rotor shafts of the motor-generators. Aspreviously discussed, when the electric drive axle have inboard oroutboard motor arrangements and their gear packaging is mirroredfront-rear, the electric motor-generators in each axle may be rotated ina similar direction in both forward and reverse drive modes. However,when the electric drive axle have inboard or outboard motor arrangementand their gear packaging is symmetric front-rear, the electricmotor-generators in each axle may be rotated in opposite directions inboth forward and reverse drive modes.

At 906, the routine includes selecting gears according to vehicleoperating conditions such as vehicle speed and electric motorefficiency. Clutch assemblies may be operated to engage and/or disengagecomponents of the gear trains to adjust a gear ratio delivered to thefront and rear drive wheels. The routine then returns to the start.

The technical effect of providing a vehicle system with multipleelectric drive axles with planetary gear sets and selectable gears it toprovide compact axle arrangements with increase gear range adaptabilityin the vehicle. Consequently, the vehicle's gearing may be selected tomore aptly suite the vehicle's driving environment.

FIGS. 2-8 show example configurations with relative positioning of thevarious components. If shown directly contacting each other, or directlycoupled, then such elements may be referred to as directly contacting ordirectly coupled, respectively, at least in one example. Similarly,elements shown contiguous or adjacent to one another may be contiguousor adjacent to each other, respectively, at least in one example. As anexample, components laying in face-sharing contact with each other maybe referred to as in face-sharing contact. As another example, elementspositioned apart from each other with only a space there-between and noother components may be referred to as such, in at least one example. Asyet another example, elements shown above/below one another, at oppositesides to one another, or to the left/right of one another may bereferred to as such, relative to one another. Further, as shown in thefigures, a topmost element or point of element may be referred to as a“top” of the component and a bottommost element or point of the elementmay be referred to as a “bottom” of the component, in at least oneexample. As used herein, top/bottom, upper/lower, above/below, may berelative to a vertical axis of the figures and used to describepositioning of elements of the figures relative to one another. As such,elements shown above other elements are positioned vertically above theother elements, in one example. As yet another example, shapes of theelements depicted within the figures may be referred to as having thoseshapes (e.g., such as being circular, straight, planar, curved, rounded,chamfered, angled, or the like). Further, elements shown intersectingone another may be referred to as intersecting elements or intersectingone another, in at least one example. Further still, an element shownwithin another element or shown outside of another element may bereferred as such, in one example.

In a first embodiment, a system includes a first electric drive axleassembly with a first gear train having a first planetary gear setaxially offset from a first electric motor-generator, wherein the firstplanetary gear set is rotationally coupled to a first differential, anda second electric drive axle assembly with a second gear train having asecond planetary gear set axially offset from a second electricmotor-generator, wherein the second planetary gear set is rotationallycoupled to a second differential. In a first example of the system, thefirst gear train includes multiple selectable gear sets rotationallycoupled to the first planetary gear set and the second gear trainincludes multiple selectable gear sets rotationally coupled to thesecond planetary gear set. A second example of the system optionallyincludes the first example, and further includes, wherein gear ratios ofthe multiple selectable gear sets in the first gear train aresubstantially equivalent to gear ratios of the multiple selectable gearsets in the second gear train. A third example of the system optionallyincludes one or more of the first and second examples, and furtherincludes, wherein the first electric motor-generator includes a firsthousing and the second electric motor-generator includes a secondhousing having a different geometric profile than the first housing. Afourth example of the system optionally includes one or more of thefirst through third examples, and further includes, wherein one or moregears in the first gear train have a manufacturing equivalency to one ormore gears in the second gear train. A fifth example of the systemoptionally includes one or more of the first through fourth examples,and further includes a first beam axle rotationally coupled to the firstdifferential and a second beam axle rotationally coupled to the seconddifferential. A sixth example of the system optionally includes one ormore of the first through fifth examples, and further includes, whereinthe first beam axle is arranged co-axial with a first output shaft inthe first gear train and where the second beam axle is arranged co-axialwith a second output shaft in the second gear train. A seventh exampleof the system optionally includes one or more of the first through sixthexamples, and further includes, wherein a first electrical interface ofthe first electric motor-generator and a second electrical interface ofthe second electric motor-generator each extend upward from a housing ofthe corresponding electric motor-generator. An eighth example of thesystem optionally includes one or more of the first through seventhexamples, and further includes, wherein the first planetary gear set ispositioned longitudinally inboard from the first electric motor andwhere the second planetary gear set is positioned longitudinally inboardfrom the second electric motor and wherein housings of the first andelectric drive axle assemblies have a mirrored geometric profile. Aninth example of the system optionally includes one or more of the firstthrough eighth examples and further includes a controller includinginstructions stored in memory that when executed, during a forward orreverse drive mode, cause the controller to rotate the first electricmotor-generator and the second electric motor-generator in oppositedirections.

In another embodiment, a method includes transferring rotational energyfrom a first electric motor-generator through a first gear train to afirst set of drive wheels, and transferring rotational energy from asecond electric motor-generator through a second gear train to a secondset of drive wheels, wherein the first gear train includes a firstplanetary gear set axially offset from the first electricmotor-generator, wherein the first planetary gear set is rotationallycoupled to a first differential, wherein the second gear train includesa second planetary gear set axially offset from the second electricmotor-generator, and wherein the second planetary gear set isrotationally coupled to a second differential. In a first example of themethod, transferring rotational energy from the first electricmotor-generator through the first gear train to the first set of drivewheels includes rotating a first rotor shaft of the first electricmotor-generator in a first rotational direction, and transferringrotational energy from the second electric motor-generator through thesecond gear train to the second set of drive wheels includes rotating asecond rotor shaft of the second electric motor-generator in a secondrotational direction opposite the first rotational direction. A secondexample of the method optionally includes the first example, and furtherincludes, wherein each of the first and second planetary gear sets ispositioned longitudinally inboard or outboard from their respectiveelectric motor-generators. A third example of the method optionallyincludes one or more of the first and second examples, and furtherincludes, wherein the steps of transferring rotational energy from thefirst electric motor-generator and the second motor-generator areimplemented during a forward drive mode or a reverse drive mode. Afourth example of the method optionally includes one or more of thefirst through third examples, and further includes transitioning betweenselectable gear sets in the first gear train, and transitioning betweenselectable gear sets in the second gear train, wherein gear ratios ofthe selectable gear sets in the first gear train are substantiallyequivalent to gear ratios of the selectable gear sets in the second geartrain.

In yet another embodiment, a system includes a first electric drive axleassembly with a first gear train having a plurality of selectable gearsets rotationally coupled to a first planetary gear set, wherein thefirst planetary gear set is axially offset from a first electricmotor-generator and wherein the first planetary gear set is directlyrotationally coupled to a first differential, and a second electricdrive axle assembly with a second gear train having a plurality ofselectable gear sets rotationally coupled to a second planetary gearset, wherein the second planetary gear set is axially offset from asecond electric motor-generator and wherein the second planetary gearset is directly rotationally coupled to a second differential, whereingear ratios of the plurality of selectable gear sets in the first geartrain are substantially equivalent to gear ratios of the plurality ofselectable gear sets in the second gear train. In a first example of thesystem, a first beam axle rotationally coupled to the first differentialand a second beam axle rotationally coupled to the second differentialand where the first beam axle is arranged co-axial to a first outputshaft in the first gear train and where the second beam axle is arrangedco-axial to a second output shaft in the second gear train. A secondexample of the system optionally includes the first example, and furtherincludes, wherein the first electric motor-generator includes a firsthousing and the second electric motor-generator includes a secondhousing has a mirrored geometric profile in comparison to the firsthousing. A third example of the system optionally includes one or moreof the first and second examples, and further includes, wherein each ofthe first and second planetary gear sets is positioned longitudinallyinboard or outboard from their respective electric motor-generators. Afourth example of the system optionally includes one or more of thefirst through third examples, and further includes a controllerincluding instructions stored in memory that when executed, during aforward or reverse drive mode, cause the controller to rotate the firstelectric motor-generator and the second electric motor-generator inopposite directions.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A vehicle system comprising: a firstelectric drive axle assembly with a first electric motor-generatorrotationally coupled to a first gear train, wherein the first gear trainis designed with multiple selectable gear sets and is rotationallycoupled to a first differential, wherein the first differential ispositioned on a lateral side of the first electric motor-generator,wherein the multiple selectable gear sets each include a gear positionedcoaxial to a first intermediate shaft that is positioned between a firstinput shaft and a first output shaft; and a second electric drive axleassembly with a second electric motor-generator and a second gear train,wherein the second gear train is designed with multiple selectable gearsets and is rotationally coupled to a second differential, wherein thesecond differential is positioned on a lateral side of the secondelectric motor-generator, wherein the multiple selectable gear sets eachinclude a gear positioned coaxial to a second intermediate shaft that ispositioned between a second input shaft and a second output shaft;wherein gear ratios of the multiple selectable gear sets in the firstgear train are substantially equivalent to gear ratios of the multipleselectable gear sets in the second gear train.
 2. The vehicle system ofclaim 1, wherein the first gear train includes a first clutch assemblyand a second clutch assembly that are positioned coaxial to the firstoutput shaft and the second gear train includes a third clutch assemblyand a fourth clutch assembly that are positioned coaxial to the secondoutput shaft.
 3. The vehicle system of claim 1, wherein one or moregears in the first gear train have a manufacturing equivalency to one ormore gears in the second gear train.
 4. The vehicle system of claim 1,wherein the first and second electric drive axle assemblies are beamaxle assemblies that are continuous structures that are profiled toaxially extend between drive wheels.
 5. The vehicle system of claim 4,wherein the first beam axle is arranged co-axial with the first outputshaft in the first gear train and where the second beam axle is arrangedco-axial with the second output shaft in the second gear train.
 6. Thevehicle system of claim 1, wherein a first electrical interface of thefirst electric motor-generator and a second electrical interface of thesecond electric motor-generator each extend upward from a housing of thecorresponding electric motor-generator.
 7. The vehicle system of claim2, wherein at least one of the first and second clutch assemblies is afriction clutch and at least one of the third and fourth clutchassemblies is a friction clutch.
 8. The vehicle system of claim 1,further comprising a controller including instructions stored in memorythat when executed, during a forward or reverse drive mode, cause thecontroller to: rotate the first electric motor-generator and the secondelectric motor-generator in opposite directions.
 9. A method foroperation of a vehicle system, comprising: transferring rotationalenergy from a first electric motor-generator through a first gear trainto a first set of drive wheels; and transferring rotational energy froma second electric motor-generator through a second gear train to asecond set of drive wheels; wherein the first gear train includes afirst clutch assembly and a second clutch assembly; wherein the firstgear train is rotationally couple to a first planetary gear set that isrotationally coupled to a first differential; wherein the second geartrain includes a third clutch assembly and a fourth clutch assembly;wherein the first clutch assembly and the third clutch assembly aresubstantially equivalent; wherein the second clutch assembly and thefourth clutch assembly are substantially equivalent; wherein the secondgear train is rotationally coupled to a second planetary gear set thatis rotationally coupled to a second differential; and wherein gearratios of the multiple selectable gear sets in the first gear train aresubstantially equivalent to gear ratios of the multiple selectable gearsets in the second gear train.
 10. The method of claim 9, wherein:transferring rotational energy from the first electric motor-generatorthrough the first gear train to the first set of drive wheels includesrotating a first rotor shaft of the first electric motor-generator in afirst rotational direction; and transferring rotational energy from thesecond electric motor-generator through the second gear train to thesecond set of drive wheels includes rotating a second rotor shaft of thesecond electric motor-generator in a second rotational directionopposite the first rotational direction.
 11. The method of claim 10,wherein each of the first and second planetary gear sets is positionedlongitudinally inboard or outboard from their respective electricmotor-generators.
 12. The method of claim 10, wherein the steps oftransferring rotational energy from the first electric motor-generatorand the second motor-generator are implemented during a forward drivemode or a reverse drive mode.
 13. The method of claim 10, furthercomprising: transitioning between selectable gear sets in the first geartrain; and transitioning between selectable gear sets in the second geartrain.
 14. A vehicle system comprising: a first electric drive axleassembly with a first electric motor-generator rotationally coupled to afirst gear train having a plurality of selectable gear sets, a firstclutch assembly, and a second clutch assembly; and a second electricdrive axle assembly with a second electric motor-generator rotationallycoupled to a second gear train having a plurality of selectable gearsets, a third clutch assembly, and a fourth clutch assembly; wherein thefirst clutch assembly and the third clutch assembly are substantiallyequivalent; wherein the second clutch assembly and the fourth clutchassembly are substantially equivalent; and wherein gear ratios of theplurality of selectable gear sets in the first gear train aresubstantially equivalent to gear ratios of the plurality of selectablegear sets in the second gear train.
 15. The vehicle system of claim 14,further comprising a first differential rotationally coupled to a firstplanetary gear set that is rotationally coupled to the first gear trainand a second differential that is rotationally coupled to a secondplanetary gear set that is rotationally coupled to the second gear trainand wherein the first differential is arranged co-axial to a firstoutput shaft in the first gear train and where the second differentialis arranged co-axial to a second output shaft in the second gear train.16. The vehicle system of claim 14, wherein the first electricmotor-generator includes a first housing and the second electricmotor-generator includes a second housing has a mirrored geometricprofile in comparison to the first housing.
 17. The vehicle system ofclaim 14, wherein each of the first and second planetary gear sets ispositioned longitudinally inboard or outboard from their respectiveelectric motor-generators.
 18. The vehicle system of claim 14, furthercomprising a controller including instructions stored in memory thatwhen executed, during a forward or reverse drive mode, cause thecontroller to: rotate the first electric motor-generator and the secondelectric motor-generator in opposite directions.